In the fourth round of the 2010 Challenge Cup, he finally made his first-grade début, after three years in reserve-grade rugby, playing on the wing in place of the injured Francis Meli, where he kicked eight goals from as many attempts in a 56–16 win over Toulouse Olympique. In his Super League début the week later, again deputising for Meli, Foster looked impressive once more with the boot scoring eight from eight in a 41–20 success over Leeds Rhinos. His first failure with the boot only came in his third appearance, when, in a 54–0 Magic Weekend win over Hull Kingston Rovers, he kicked only two from six, whilst also scoring his maiden try for the club. He missed the cut for the Challenge Cup game against Harlequins RL, but thanks to a recurrence of Meli's injury, Foster returned for the 34–42 loss at Salford City Reds, in which he was brought off the field after ten minutes after a poor display defensively.
However, this did not end his run in the first team, as he started on the wing against Rovers in a 68–12 win, before being dropped for the loss at Hull FC. However, he returned to play on the right wing in a 24–22 win at home to Huddersfield, where he kicked five goals. The next week (in round 18) he was again on the wing for a 24–26 win over rivals Wigan Warriors, where he kicked three from five and scored a try. He missed three games with a calf knock but returned for Saints in a centre role against Wakefield that saw him kick seven goals from nine attempts. He was also part of beaten finalists St. Helens where Wigan Warriors won 22–10 in the 2010 Super League Grand Final.
In 2011 Jamie has so far scored 14 tries and 77 goals, a total of 210 points, in 13 appearances and 3 from the bench. His partnership with Francis Meli this season has been productive. In the first game of the 2011's Super League XVI St. Helens played Wigan Warriors in a repeat of the Super League final. In this game Saints were losing 16–0 at halftime and came back to draw 16–16 with Jamie coming off the bench to kick 2 goals. Foster then kicked 8/10 against Salford City Reds in round 2. When Saints played Leeds Rhinos, in Round 6, he scored 2 tries, including a round the back trick to score in the corner, and kicked 5 goals. In Round 12, he kicked a touchline goal to win the game for Saints against Castleford Tigers. In the Challenge Cup Fifth Round Jamie kicked 11 out of 12 goals in a 70–0 thrashing of Featherstone Rovers.
Royce Simmons, the Saints coach, has said "Jamie Foster's ability to kick points is vital to the Saints. The way Foster can turn four points into six, he can break the heart of another side through that." Jamie is the fourth top try scorer in Super League with 12 tries, and is the fifth top goal scorer with 58 successful kicks.
Near the end of the 2012 Super League season, Jamie spent a month on loan at Hull F.C.. His first game for the Black and Whites was against arch-rivals Hull Kingston Rovers, he helped his new side to a 32–18 win by kicking 6 goals. The week after he played in the 36–24 win against Salford City Reds where he kicked 100% of his goals with 7 goals from 7 attempts. He was also part of the team which lost 48–10 to Wigan Warriors, Foster managed to get himself a goal in this game. Jamie was on form the next week against Catalans Dragons where he recorded his first try for Hull FC and also kicked 5 goals leading his team to a 30–10 win. However, this victory was short lived as the Black & Whites were soundly beaten 42–16 by newly promoted Widnes Vikings, Foster got himself on the scoreboard with 2 goals. He was a key member in Hull F.C.'s record breaking 70–6 win against his future club the Bradford Bulls, he helped his team to this huge win by contributing 2 tries and 9 goals which meant Hull were secure in the playoffs. His last regular season game for Hull was in a 36–10 win over Castleford Tigers, Foster put in a fine display and kicked all 6 goals.
Jamie signed for Super League side Bradford Bulls on a 1 Year Deal.
2013 – 2013 Season
Foster featured at fullback for the pre-season friendlies against Dewsbury Rams and Leeds Rhinos. He scored against Dewsbury Rams (8 goals) and Leeds Rhinos (4 goals).
He featured in five consecutive games from Round 1 (Wakefield Trinity Wildcats) to Round 5 (Huddersfield Giants). He was injured for Round 6. Foster featured in four consecutive games from Round 7 (Hull Kingston Rovers) to Round 10 (Salford City Reds). Foster was injured for Round 11–15 but returned for Round 16 (Huddersfield Giants). Jamie missed Round 17–19 due to injury. He returned in Round 20 (Warrington Wolves) to Round 27 (Huddersfield Giants). Foster featured in the Challenge Cup against Rochdale Hornets. He scored against Wakefield Trinity Wildcats (2 tries, 9 goals), Hull F.C. (5 goals), Castleford Tigers (12 goals), St. Helens (1 goal), Huddersfield Giants (2 tries, 17 goals), Hull Kingston Rovers (1 try, 5 goals), Catalans Dragons (4 goals), Leeds Rhinos (3 goals), Salford City Reds (4 goals), Rochdale Hornets (2 goals), Warrington Wolves (2 goals), Wigan Warriors (4 goals) and London Broncos (1 goal).
He re-signed with the Bulls for 2 years midway through the season.
2014 – 2014 Season
Foster featured in the pre-season games against Hull F.C., Dewsbury Rams and Castleford Tigers. He scored against Hull F.C. (1 try, 5 goals) and Castleford Tigers (1 goal).
He featured in Round 1 (Castleford Tigers) to Round 5 (Huddersfield Giants). Foster missed Rounds 6–7 due to injury. He featured in Round 8 (Salford Red Devils) then in Round 11 (Warrington Wolves) to Round 14 (Catalans Dragons). He was injured for Round 15–19. Foster played in Round 20 (St. Helens) to Round 21 (Huddersfield Giants) then in Round 24 (Hull F.C.). His final game for Bradford was in Round 27 (London Broncos). Jamie featured in Round 4 (Oldham Roughyeds) to Round 5 (Catalans Dragons) in the Challenge Cup. He scored against Castleford Tigers (1 try, 3 goals), Wakefield Trinity Wildcats (3 goals), London Broncos (11 goals), Hull F.C. (1 try, 7 goals), Huddersfield Giants (2 tries, 8 goals), Oldham Roughyeds (1 try), Salford Red Devils (1 try), Catalans Dragons (3 tries, 6 goals), Warrington Wolves (1 try, 5 goals) and St. Helens (1 try, 3 goals).